Ethylene-vinyl ester pour depressant for middle distillates



Aug 7, 1962 s n NYcKYJ Erm. 3,048,479

ETHYLENE-V'INYL ESTER POUR DEPRESSANT Y FOR MIDDLE DISTILLATES Flled Aug. 3, 1959 6 Sheets-Sheet 1 ID N I5 VINYL. ACETATE IN SOLVENT, WT.

FIGURE I COPOLYMERIZATION OF ETHYLENE AND VINYL ACETATE CONTENT OF VINYL ACETATE IN COPOLYMER VS CONCENTRATION OF VINYL ACETATE IN SOLVENT o o Oosfago STEPHAN ILNYCKYJ CHARLES B. RUPAR 'NVENTORS www PATENT ATTORNEY SV.IIL.NYCKYJ ETAL Aug. 7, 1962 3,048,479 ETRYLENE- NYL. ESTER POUR DEPRESSANT FOR MIDDLE DISTILLATES 6 Sheets-Sheet 2 Filed Aug. 3, 1959 OOON O09 OOO- 06m O O S l N E V m M N JR u wmf V CU 9% WR 1 h. wv... NMM7 l A 0/ N HU. o @m TH w O SC Y M B C ONM- M n Om N MIDOE PATENT ATTORNEY ASTM POUR POINT, F.

Aug- 7, 1952 s. lLNYcKYJ ETAL 3,048,479

ETHYLENE-VINYL ESTER POUR DEPRESSANT FOR MIDDLE DISTILLATES Filed Aug. 3, 1959 6 Sheets-Sheet 3 FIGURE 3 EFFECT OF VINYL ACETATE CONTENT OF COPOLYMER l l 0 0.l 0.2 0.3 0.4 0.5 COPOLYMER, WT.

INVENTORS PATENT ATTORNEY Aug- 7, 1962 s. H NYCKYJ ET AL 3,048,479

ETHYLENE-VINYL ESTER POUR DEPRESSANT FOR MIDDLE DISTILLATx-:s

Filed Aug. 5, 1959 6 Sheets-Sheet 4 FIGURE 4 EFFECT OF VINYL ACETATE CONTENT ON POUR DEPRESSING POTENCY OF COPOLYMER POUR DEPRESSION, F.

| i o lo 2o 30 4o 50 VINYL ACETATE IN COPOLYMER, w12

STEPHAN ILNYCKYJ INVENTORS BWM/.(27%

PATENT ATTORNEY ASTM POUR POINT F.

Aug 7, 1962 s. n NYcKYJ ETAL 3,048,479

ETHYLENE-VINYI.. ESTER POUR DEPRESSANT FOR MIDDLE DISTILLATES Flled Aug. 5, 1959 6 Sheets-Sheet 5 FIGURE 5 EFFECT 0F MOLECULAR WEIGHT OF COPOLYMER STEPHAN ILNYCKYJ CHARLES B RUPAR INVENToRs BYZMYVMMQ PATENT ATTORNEY FIGURE 6 POTENCY OF ETHYLENE POLYMERS AS POUR DEPRESSANTS FOR MIDDLE DISTILLATE FUELS Aug 7 1962 s. Il NYcKYJ Er 0 ETHYLENE-VINYL ESTER POUR QPRESSANT 3 48479 FOR MIDDLE DISTILLATES Filed Aug. 3, 1959 6 Sheets-Sheet 6 O5 0.6 POUR DEPRESSANT, WT.

COPOLYMER OF ETHYLENE AND VINYL ACETATE POLYETHYLENE A PoLYETHYLl-:NE B

O O O N s anod wlsv STEPHAN ILNYCKYJ CHARLES -B RUPAR INVENToRs Mil/.(27%

PATENT ATTORNEY United States Patent Utilice 3,048,479 Patented Aug. 7, 1962 3,048,479 ETHYLENE-JENYL ESTER POUR DEPRESSANT FR MIDDLE DISTILLATES Stephan llnyeiryj and Charles B. Rupar, Sarnia, ntario, Canada, assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Aug. 3, 1959, Ser. No. 331,244 6 Claims. (Cl. 44-62) The present invention relates to improving the flow of low temperatures and the pour point characteristics of middle distillates. More particularly, the present invention relates to the preparation of improved low cold test hydrocarbon fuels, in particular heating oils and diesel fuels, kerosine, aviation turbo-jet fuels and other fuels that are subject to low temperatures.

The present application is a continuation-impart of application Serial No. 719,188, filed March 5, 1958, entitled Pour Depressant for Middle Distillates, now abandoned, for the same inventors.

With the increase in the use of hydrocarbon fuels of all kinds, a serious problem has arisen in areas frequently subjected to low temperatures in the cold characteristics of fuels. Particularly, serious problems have been encountered by heating oils and diesel and jet fuels that have too high a pour point, resulting either in distributional or operating difficulties or both. For example, the distribution of heating oils by pumping or syphoning is rendered difficult or impossible at temperatures around or below the pour point of the oil. Furthermore, the flow of the oil at such temperatures through the filters cannot be maintained, leading to the failure of the equipment to operate.

Also the low temperature properties of petroleum distillate fuels boiling in the range between about 250 and about 750 F. have attracted increasing attention in recent years because of the growth of markets of such fuels in subarctic areas and because of the development of turbo-jet aircraft capable of operating at altitudes Where temperatures of 50 F. or lower may be encountered.

It is, of course, well known to add pour depressants to lubricating oils to lower the pour point. These lube oil additives, mostly high molecular weight organic compositions formed by alkylation of benzene or naphthalene or derivatives thereof or by polymerization of lower molecular weight methacrylates, or by condensation polymerization of various kinds, are not satisfactory in service with middle distillate and lighter fuels. Poor performance of these additives might possibly result from the structural diiferences between waxes occurring in lubricating oils and so-called middle distillates.

A wide variety of compounds have been found to be effective as pour point depressants for lubricating oil. Among the best known are Paraflow, Santopour and Acryloid and their modifications. They are prepared either by condensing aromatic compounds with long chain parafins, such as wax, or by condensing olenic esters. It is generally considered that these pour depressants are effective in that in cooling an additive-containing oil, the hydrocarbon chain of the additive becomes incorporated into the crystal lattice of the separated wax, while the other part of the pour depresant molecule prevents the crystals from adhering together to form a gel structure. The failure of these additives to be effective in middle distillates may at least in part be due. to the basic difference in the composition between the wax in lubricating oils and that in middle distillate fuels.

Itis, therefore, the principal object of the present invention to set forth an improved pour depressant for middle distillate and lighter fuels. In general, these oils boil in the range from about 250 to 750 F.

It is a still further object of the present invention to provide heating oils, diesel fuel oils, kerosines and jet fuels having low pour points. Such fuels include aviation turbo-jet fuels, kerosines, diesel fuels, and heating oils. Aviation turbo-jet fuels in which the polymers may be used normally boil between about 250 and about 550 F. and are used in both military and civilian aircraft. Such fuels are more fully defined by U.S. Military Specifications MIL-PLS 624C, MIL-F-25554A, MIL-F- 25558A, and amendments thereto. Kerosines and heating oils will normally have boiling ranges between about 300 and about 750 F. and are more fully described in ASTM Specification D-396-48T and supplements thereto, Where they are referred to as No. 1 and No. 2 fuel oils. Diesel fuels in which the polymers may be employed are described in detail in ASTM Specification D97535T and later versions of the same specification.

The polymeric pour depresants may, in accordance with the invention, be employed in conjunction with a variety of other additives commonly used in fuels such as those set forth above. Typical of such additives are rust inhibitors, anti-emulsifying agents, corrosion inhibitors, antioxidants, dispersants, dyes, dye stabilizers, haze inhibitors, antistatic agents and the like. It will frequently be found convenient to prepare additive concentrates for use in the various types of fuels and thus add all of the additives simultaneously.

Other and further objects of the present invention will appear more clearly hereinafter.

The pour depressant comprises ethylene-vinyl acetate copolymer. It is preferred that the parts by weight of ethylene in the copolymer be in the range from about 60 to 99% as compared to parts by weight of vinyl acetate in the range from about 40 to about 1%. A very desirable ethylene-vinyl acetate copolymer contains about 15 to 25% by weight of vinyl acetate, as for example, about 20% parts by weight of vinyl acetate.

The molecular weights of the ethylene-vinyl acetate copolymer are critical and should be in the range from about 1,000 to 3,000, preferably, in the range from about 1,500 to 2,200. The molecular weights are determined by K. Rasts method (Ber. 55, 1051, 3727 (1922)).

The ethylene-vinyl acetate copolymer as described above is used in a concentration in the range from about .001 to .5% by weight, preferably, in a concentration in the range from about .005 to .1% by weight.

Surprisingly, these low molecular weight copolymers have no effect upon the pour points of lubricating oils, thus emphasizing the difference in structure between the wax associated on the one hand with lube oils and on the other with middle distillates. The low molecular Weight copolymers may be prepared by any peroxide process. In some instances, it may be desirable to first prepare a higher average molecular weight polymerization product and then recover from that product material having a molecular weight within the range between about 1,000 and about 3,000. Since such polymerization products normally consist of a smear of polymers whose molecular Weights vary over a wide range, an effective method `for recovering the 1,000 to 3,000 molecular Weight portion therefrom is to extract the product with a solvent such as normal heptane or methyl-ethyl ketone. Other methods for obtaining the low molecular weight materials include thermal degradation lof the high molecular Weight polymer or treatment of the high molecular weight polymer with ozone in order to break the polymer chains. Still other methods also useful will be apparent to those skilled in the art.

A very desirable method is to conduct polymerization in :a benzene solution using di-tertiary-butyl-peroxide as an initiator at a temperature in the range from about 280 to 340 F. The preferred temperature is about 300 F. The pressure is in the range from about 700 to 2,000 pounds, preferably, at about 800 pounds. The autoclave or similar equipment containing the solvent, initiator and vinyl acetate is purged about three times with nitrogen, twice with ethylene `and then charged with a sufcient amount of ethylene to yield the desired pressure when heated to the reaction temperature. During the polymerization additional ethylene is `added Whenever the pressure drops by about 100 p.s.i.g. Polymerization is considered complete when it is less than 50 p.s.i.g. pressure drop per hour. The product is stripped free of solid and unreacted vinyl Iacetate under vacuum.

A typical distillate fuel boiling in the range from 250 to 750 F. to which the present additives may be added are middle distillate heating oils. These fuels are of commercial grade and have typical properties as follows:

The improvements obtained by adding the additives in accordance with the present invention are set forth in the following table. All pour points quoted hereafter were obtained Lby ASTM Method D-97-47.

A number of tests were conducted using various polymers in a 50-50 blend of virgin gas oil and cracked gas oil. The virgin gas oil boiled in the range from about 350 to 700 F., and the cracked gas oil boiled in the range from about 350 to 650 F. The blend had a pour of +*7 F. The various polymers were prepared under varying pressure `and other varying operating conditions. As pointed out heretofore, the critical factors with respect to desirable polymers are molecular Weights and the concentration of the vinyl acetate in the polymer. The results of these tests are shown in the following table:

TABLE I 40%, the effectiveness of the additive is greatly decreased (runs No. 9 and 10).

Reference is made of FIGURE l which shows that at a constant pressure, the percentage of vinyl `acetate in the copolymer increases with increasing concentration of this chemical in the solvent. The copolymerization was carried out at a pressure of 750 p.s.i.g., at a temperature of 300 F., utilizing benzene as 'a solvent and di-tertiarybutyl-peroxide as the initiator.

Reference is made to FIGURE 2 which illustrates that `at a constant concentration of vinyl acetate in the solvent, the ratio of vinyl acetate in the polymer decreases with increasing partial pressure of ethylene. The concentrations of the vinyl acetate utilized in the solvent were: 0.2 Wt. percent; 2.1 wt. percent and 6.3 Wt. percent. Other conditions were identical with those specified with respect to FIGURE l.

Reference is made to FIGURE 3 which shows the potency of the copolymers as pour depressants for middle distillates. The middle distillate was identical With that specified with respect to Table l. Curves A, B, C, D, E and F correspond to run Nos. 9, 10, 2, 3, 1 and 13, respectively of Table I. It is to be noted that curve F, containing about 20% of vinyl acetate was very effective.

Reference lis made to FIGURE 4. This gure illustrates the relationship of the potency of the pour depressants to their vinyl acetate content. Curve A contains .05% pour depressant, Whereas, curve B contains 0.1% pour depressant. It is to be noted that the most potent pour depressant was obtained lat 850 p.s.i.g. when the copolymer contained about 80% ethylene and 20% vinyl acetate. It is to be noted from FIGURE 4 that copolyllyrners containing more than 20% vinyl acetate show a drop in pour depressing activity. This is particularly pronounced at lowe concentration of the additive. At 0.05% concentration, the activity of pour depressants becomes negligible when the copolymer contains about 24% of vinyl acetate. At 0.1% concentration, Ithe copolymers show some pour depressing activity until the vinyl acetate amounts to about 35% of the total polymer.

Reference lis made to FIGURE 5 Which illustrates the etfect of pressure at which the copolymer is produced on its activity as pour depressants. The polymers obtained at pressures lower than about l600 p.s.i.g. show little promise as pour depressants. As the molecular weight is proportional to pressure during the synthesis, this illus- Synthesis of Copolymers of Ethylene and Vinyl Acetate [Conditions of polymerization: 300 F., d-tert-butvlperoxide initiator, benzene solvent] ASTM Pour P0int.1 F.

Vinyl Acetate Cone., Yield Run Wt. Percent Pressure, grams No. p.s.i.g. per gram Peroxide in Benzene in Product 0.05% 0.1%

7.5 0 -25 Nil Nil 750 19 +5 0 .53 3.0 750 18 +5 0 2.1 8. 4 750 17. 5 0 -10 8. 5 28.1 750 22. 5 +10 +25 2.1 5.8 900 23 0 -20 2.1 17. 9 400 9 +15 +10 2.1 12.1 600 14 +15 5 21. 0 53. 8 750 31 +20 +20 14. 8 44. 7 750 26 +15 +15 11.7 35.2 750 23 5 +10 +10 6. 3 24. 3 750 18 +10 -50 6. 3 20. 4 850 23 -40 -70 6.3 14. 7 1, G00 29. 5 -10 -70 From the above, it is apparent that 3% vinyl acetate 70 trates that the copolymer must have a certain minimum molecular Weight to be effective as pour depressants.

Reference is made to :FIGURE 6 which illustrates the effectiveness of the copolymer of the present invention is much superior to an ethylene polymer containing no vinyl acetate in the monomer (run No. 3 vs. run No. 2). It is also apparent that a concentration of vinyl acetate approximately of 28% is very eifective (run No. 5), and

All

that when the vinyl acetate concentration exceeds about polymers used had a molecular Weight of about 1,300.

The pour depressant 'for middle distillate fuelshas little effect on oil viscosity, particularly in the concentration ranges in which it is effective. This is clearly shown in Table 1H.

TABLE Il Effect of Ethylene Vinyl Acetate Copolymcr on Pour Point and Viscosity of LightGas Oil [ASTM prn 0010i 0ft110 011; +25 1a.]

Weight Pour Point Viscosity of Percent Depression, Oil 100, EthyleneCo- SUS polymer (1) (1) 800 molecular Weight as determined by Rast Method.

TABLE HI List of Hydrocarbons Found Inejjecive as Pour Depressants for ldiddle Distillotes Wt. Pour De- Hydrocarbon Percent pression Remarks in oil 0 1 Microcrystalline Waxes:

. 1\/1.P.1s0 F g1 1. 0 -8 112.185 F 0693+ g 0.001 -l M11. 115 F gj g1 1.0 0.001 -3 9 MP. 118 F Ofi *5 1.0 -ll Visc. 100, SUS

0. 1 2 0 34. 9 0.1 2 +5 14g. 80 Pol ro lencs 0.1 2 +5 1 .9

yp py 0. 1 i +2. 5

S0110, M01. Wt. :1i-C1 sol. linear Polypropylenel I 'l2 5 Range, 10,000-

Iol butenes Indopo1): ASTM Mol. y Pour, F. Wt.

TABLE IIL-Continued Wt. Pour De- Hydrocarbon Percent pression Remarks in oil F. 1

0.1 +5 Low Viste. Oil.

r Polybutene-l gj +22 2;

` 0.1 +7.5 Viso. at F.

1,269 SUS.

Visc. at 100 F.,

SUS

0.1 +5 31.0 0. +5 7 .10 Po1ybutene-2 0. l 0 841* 2 0.1 +2. 5 1, 405.0 Polyisobutylene:

0.001 Fg f. 0.01 Mol. Wt. 20,400 0.1 o 1.0 0 0. 001 0 M01. Wt. 100,000 0.g0 g M01. Wt. 200,000 M01. Wt. 300,000.- (3) Polycyclopentane Viso. at 100 F.

6, 340 SUS.

No'rn.-Polystyrenes-None of several grades tried was soluble in oil. (1) Pour Depression.

Pour Elevation. 2 Liquid. 3 Insoluble in Oil.

It has hitherto been pointed out that wax in middle TABLE IV Effect of Various Additives on ASTM and Stable Pour Points of a 356 to 682 F. Virgin Gas Oil (l) As determined by Rast Method.

These data clearly demonstrate the superiority of the low molecular weight ethylene-vinyl acetate copolymers over the lubricating oil pour depressants. On the other hand, when these copolymers are added. to lubricating oils, they in turn are ineffective.

TABLE V Weight ASTM Cloud/Pour, F. Percent Oopolymer(Mol. MCT-101 MCT-301 MCT-601 lParaHinic type obtained from Leduc crude by distillation, dewaxing, phenol extraction and clay treatment.

It is probable that the different eiects of these copolymers on pour of lubricating oils is due at least in part to the structural dilerences between waxes in middle proved in pour point, as shownin Table VI.

TABLE VI Response of `Virgin and Cracked Gas Oz'lto Polyethylene '1f Vinyl Acetate Copolymer Pour Depressant Y i 'l mv. m01. ve-soo 11 1 As determined by Rast method.

2 Boilingy range 442-674 F.

3 Boiling range 394-038 F.'

4 Less than. I

The effectiveness of the low molecular weight ethylenevinyl acetate copolymersas pour depressants for jet fuels is shown in Table Vll below.v Jet fuels are subject to extreme temperature conditions, and it is 'highly important that they have low pour and freezingpoints. For comparisonA are shown values of customary pour. depressants such as Paraow, a condensation productl of chlorinated wax and naphthalene; Acryloid, a polymer of methyl methacrylate; and OA-142, a copolymer of alkyl fumarate and vinyl acetate. Jet fuels are selected hydrocarbon fractions boiling in the naphtha and kerosine boiling range.

TABLE Vil Pour Depressants for Jet Fuels lPour Point, Freezing F. Point (FSM), F.

Jet Fuel -65 to -70 -57. 5 Jet Fuel.5% copolymer 1 Y -4-l10 #60 J et Fuel" 1% Copolymer -95 -58 J et Fuel 05% Copolynier". V 90 -00 J et Fuel" 025% Copolyrner -80 -59 J et Fuel.0125% Copolymer -75 -59 J et Fuel-4% Paralow.- L95 -58 Jet Fuel-.5% Paraovv -85 J et Fuel-1% Oft-142 Jet Fuel" 5% OA-l42 -75 Jet Freek-.25% OA-142 -75 .T et Fuel-125% Ort-142 -76 1 800 Molecular Weight as determined by Rast Method.

The effectiveness of the present ethylene-vinyl acetate copolymers with respect to increasing lterability is shown 8 by the following table. Various percentages of different substances were added to a heating oil and the iilterability determined by the Hagemann and Hammerich Test reported in DTN-51770 (Bestimmung der Filtrierbarlieit von Diesel Kraftstoffen). A mesh screen was employed.

TABLE VIII Base oil +25 +0.5% Acryloid +15 |2.0% Paraflow -28 +0.1% Ethylene-vinyl acetate copolymer (molecular weight about 1,000) -37 What is claimed is:

l. A petroleum distillate fuel composition having an improved pour `which comprises essentially a petroleum distillate fuel having a boiling range between about 250 F. and about 750 F. which has been improved with Vrespect to pour point by the incorporation therein of a pour depressing effective amount in the range from about .001 to .5% lby `weight of an oil solublefcopolymer of ethylene and a vinyl fatty acid ester having from about 3 to about 5 carbon atoms inthe ester, said copolymer having a molecular weightin Ithe rangefromfabout- 1000 to 3000, said coplymer being further characterized by containing from about 15 to 25% by weightcf said vinyl fatty acid ester. n, v

2. A petroleum distillate composition having an improved pour which comprises essentially a petroleum distillate fuel having a boiling range between about 250 F. and about 800 F. which has been improved with respect to pour point by the incorporation therein ofa pour depressing eifective amount in the range from about .01 to about 0.25% by weight of an oil soluble copolymer of ethylene and a vinyl fatty acid ester having from about 3 to about 5 carbon atoms in the ester, said copolymer v having a molecular Weight in the range from about 1000 to 2500, said copolymer lbeingfurther characterized by containing from about 15 to about 28% by Weight of said vinyl fatty acid ester.

3. Fuel composition as defined by claim 1 wherein said vinyl ester is a vinyl acetate.

4. Fuel composition as defined by claim 3 wherein said copolymer is present in a concentration from about .005 to 0.1%.

5. A fuel composition as defined `by claim 1 wherein said copolymer has a molecular weight between about 1,600 and about 2,000 and wherein said copolymer is present in a concentration from about.005 to 0.1% by weight.

6. Fuel as defined by claim l wherein said copolymer iis a coplymer of ethylene and vinyl acetate wherein the copolymer contains about 20% by weightof vinyl acetate.

References Cited in the le of this patent UNITED STATES PATENTS 

1. A PETROLEUM, DISTILLATE FUEL COMPOSITION HAVING AN IMPROVED POUR WHICH COMPRISES ESSENTIALLY A PETROLEUM DISTILLATE FUEL HAVING A BOILING RANGE BETWEEN ABOUT 250*F. AND ABOUT 750*F. WHICH HAS BVEEN IMPROVED WITH RESPECT TO POUR POINT BY THE INCORPORATION THEREIN OF A POUR DEPRESSING EFFECTIVE AMOUNT IN THE RANGE FROM ABOUT .001 TO .5% BY WEIGHT OF AN OIL SOLUBLE COPOLYMER OF ETHYLENE AND A VINYL FATTY ACID ESTER HAVING FROM ABOUT 3 TO ABOUT 5 CARBON ATOMS IN THE ESTER, SAID COPOLYMER HAVING A MOLECULAR WEIGHT IN THE RANGE FROM ABOUT 1000 TO 3000, SIADD COPLYER BEING FURTHER CHARACTERIZED BY CONTAINING FROM ABOUT 15 TO 25% BY WEIGHT OF SAID VINYL FATTY ACID ESTER. 